The investigators request the acquisition of a system for the measurement of movement (an OPTOTRAK system to be used in studies of human adults and infants and nonhuman primates (rhesus monkeys). The major users of the equipment are in the Department of Psychology and Center for Neural Science at New York University, and all have worked on aspects of perception and perceptual-motor control. Their approaches and perspectives range from single-cell physiology (Glimcher) to psychophysics (Landy, Maloney) to developmental motor control (Adolph). In each case, the major users have ongoing research projects that would be substantially enhanced by the ability to accurately record movements using the OPTOTRAK system. These projects include analyses of (1) flexible locomotor and postural responses to varying task demands in infants and adults (Adolph, Marin); (2) the responses of neurons in substantia nigra to reinforcement of motor responses whether those responses be an eye or a limb movement (Glimcher); (3) the weights given to different sources of 3-D scene information for perceptual judgments and motor responses to determine whether 3-D representations are shared for vision and action (Maloney, Wolfe); and (4) the cues to distance and viewing geometry used to scale visual cues to size, depth and shape for both vision and action (Landy).